1. I used to go swimming every Thursday when I was at schoo.

- used to V : đã từng làm gì ( thói quen quá khứ nay không còn)

2. Mai went to school on foot when she was in primary school.

- Quá khứ đơn - when she was in primary school

(+) S + Ved/V2

- walk (to place) = go (to place) on foot

3. How about cycling to the town at the weekend?

- How/What about + Ving = Why don't we + V?

4. It's about 2 kilometres from my house to the nearest bookstore.

- It's about + khoảng cách (km) from "Place 1" to "Place 2" 

= The distance between "Place 1" and "Place 2" is about + khoảng cách (km)

1. I used to swimming (đến hết) used to+v1(+)
                                                     didnt use to +v1(-)
                                                    Did+S+ use to+ v1(?)
                                                              chỉ việc ( đã từng) lm j đó
2. Mai went on foot (đến hết) vì went on foot là đã đi bộ

3.How about cycling ... đến hết( How about+v-ing)

4.
It's about 2 kms from my house to the nearest bookstore( vì between là ở giữa nên chọn khoảng từ chỗ này đến chỗ kia là hợp lí)